Method of separating hydrocarbons



May 3, 1949. G. 1 GUDENRATH METHOD OF SEPARATING HYDROCARBONS 3Sheets-Sheet 1 Filed May 12, 1945 IN V EN TOR.

M HZ 3 Sheets-Sheet 2 May 3, 1949- G. l.. GUDENRATH METHOD OF SEPARATINGHYDROCARBONS Filed may 12, 1945 N .ma

N l NNW INVENTOR.

May f3, 1949. G. l.. GUDENRATH METHOD OF SEPARATING HYDROCARBONS 5Sheets-Sheet 3 Filed May l2, 1945 do .5E

k mi WN do rui mm do 5mi. n .zo mu r|| llll IIIIIIIIL Patented May 3,1949 UNITED sTATEs PATENT oFFicE- 2,468,750 METHOD or SEPARATINGnYnRocARBoNs l George Louis Gudenrath, Houston, Tex., assignor to HudsonEngineering Corporation, Houston, Tex., a corporation of TexasApplication May 12, 1945, serial No. 593,490

4 Claims.

A higher carbon atoms to the molecule, then raise the pressure of theremaining gas to the original well pressure and pump or cycle it backthrough the well into the rock formation.

At high pressures great difculty is encountered in separating methanefrom the other constituents Without leaving a relatively high percentageof ethane, propane and some butane in the gas after it has passedthrough the absorption system. Further the absorption oil often retainsa relatively large amount of methane some of which is condensed with theheavier hydrocarbons and becomes a part of the hydrocarbon distillate tobe fractioned. The partial pressure of methane makes the fractionationcomplicated and quite expensive. Ethane and propane are valuableproducts and it is desirable to recover them from a gas mixturecontaining a higher percentage of methane.

Most natural gas contains natural gasoline and is treated in absorptionplants for the recovery of ethane, propane, butanes, pentanes andgasoline. Also the gases from petroleum distillation plants and oilcracking plants are treated in absorption and distillation units toseparate the hydrocarbons containing C2 and higher carbon atoms to themolecule for the manufacture of fuel and chemical products.

The primary object of the present invention is to providea method ofimproving the selectivity of the recovery of heavier and more desirablehydrocarbons from gas with respect to the lighter less desirablehydrocarbons, such as methane or hydrocarbons having a high vaporpressure.

A further object of the present invention is to provide a method ofeffectively absorbing the hydrocarbons having more than one carbon atomto the molecule out of natural gas and effectively separating themethane from the absorption oil and the other absorbed hydrocarbons. v

Another object of the invention is to provide a method of absorbinghydrocarbons from gas and separating methane from the heavierhydrocarbons and menstruum without heating the absorbing menstruum orhydrocarbon'mixture.

A further object of the invention is to provide a method of absorbinghydrocarbons from gas in an oil menstruum while separating methane fromthe rich menstruum and obtaining the maximum recovery of ethane, andheavier hydrocarbons.

With these and other objects in View the invention consists in themethod of absorbing hydrocarbons from gas in an absorption menstruum andseparating methane therefrom, whichV is hereinafter described andparticularly defined in the appended claims.

The various features of the invention are i1-` lustrated in theaccompanying drawings in which Figure 1 is a diagrammatic flow sheet ofan apparatus particularly adapted for absorbing the hydrocarbons fromhigh pressure gas obtained in a recycling system in which condensateisrecovered from the gas before the hydrocarbons of Figure 1 is adaptedwherein the absorption can be effected in two diiTerent pressure stages.

Figure 3 is a diagrammatic ow sheet of an apparatus wherein thehydrocarbons may be absorbed in a menstruum under a pressure which is aslow or lower than the pressure under which the menstruum may bedistilled to separate the absorbed hydrocarbons and at the same timeeliciently separating the methane from the menstruum and separatedhydrocarbons; and

Figure 4 is a diagrammatic view of an apparatus in which a method ofabsorbing hydrocarbons simultaneously from a lean gas and a rich gas maybe carried out while effectively separating methane from the absorbingmenstruum and the separated hydrocarbons.

Throughout the specification and claims the hydrocarbons are referred toas C1, C2 and higher is introduced into the top of the tower through aline I8. The volume and temperature of the absorption oil is such thatwhen the gas which may be at the high pressure existing at the well,

In absorbing the C2 and higher hydrocarbons the absorption oil becomessaturated with methane. It is important therefore that the methane beseparated because methane is troublesome during the rich oildistillation and also during the fractionation to separate theindividual hydrocarbons.

When the gas is being treated under high pressures from 1000 to 3000lbs. per square inch, it is dimcult to reduce the pressure of the gas ina single stage and still effectively separate the methane and recoverthe C2 and higher hydrocarbons. Accordingly the rich oil from the bottomof absorption tower I6 passes through an expansion valve 24 and ilowsthrough a line 26 into a ash tank 28. The hydrocarbon vapors which areseparated in the tank 28 are composed of C1, C2 and higher hydrocarbonsand flow through a line 38 into the lower portion of a reabsorptiontower 32 and pass upwardly through a body of absorption oil which isintroduced into the top of the reabsorber through a line 34. In thereabsorber substantially all of the C2 and higher hydrocarbons areabsorbed in the oil and methane passes out through a line 36 andpressure reducing valve 38.

' Simultaneously with this operation the condensate from the separatorI2 flows through a pressure reducing valve 48 and line 42 into a flashtank 44 where lower boiling hydrocarbon vapors are released. Thesevapors ow through a line 45 and join with the vapors in line 30 to passinto the bottom of the reabsorption tower 32.

The rich oil from the flash tank 28, which is saturated at its pressurewith methane, passes through a line 46 and is introduced into the bottomof an absorption section of an absorber and concentrator tower 48. Thepressure on the rich oil is reduced through a valve 58 so that the oilexpands to relase C1, C2 and some heavier hydrocarbon vapors. The C2 andheavier hydrocarbon vapors are absorbed in an absorption oil whichpasses downwardly through the tower 48 after being introduced through aline 52.

Simultaneously with the introduction of rich oil from the tank 28condensate from the tank 44 passes through a pressure reducing valve 54and line 56 into an expansion tank 58 wherein the pressure is reduced tothe pressure or slightly higher pressure than the pressure existing inthe tower 48. The pressure existing in the tower 48 is comparativelylow, that is for example from 50 to 200 lbs., and is such that themethane may be effectively removed from the absorption oil in the towerbefore the rich oil from the tower 48 is passed to a still for removingabsorbed hydrocarbons from the rich oil. Rich oil leaves the bottom ofreabsorber 32 through an'expansion valve 51 and iiows into the tower 48through the line 46. The vapors separated in the tank 58 pass through a.line 68 to join with the rich oil passing through the line 46 and flowinto the bottom of the absorption section of tower 48. The vapors fromthe rich oil and condensate pass upwardly through the tower 48 wheresubstantially all the C2 and higher hydrocarbons are absorbed andsubstantially all the methane passes out from the top of the towerthrough a line 62 and` valve 64.

Since the rich oil and vapors introduced through the lines 46 and 68 maycontain some methane it is important to remove this methane from therich oil before the rich oil leaves the tower 48. To accomplish this therich oil leaving the absorption section of tower 48 passes downwardlythrough a stripping section located below the inlet of the line 60. Nearthe bottom of the concentrating section hydrocarbon vapors con-v tainingsome C1 and substantial quantities of Czand higher hydrocarbons areintroduced through a line 66. These vapors pass upwardly through theabsorption oil and displace methane in this absorption oil with C2 andhigher hydrocarbons and carry the methane upwardly through the tower 48.By the time the rich oll reaches the bottom of the stripper section atthe bottom of the tower 48 substantially all of the methane has beenremoved. This rich oil is then drawn out through a pump 68 andcirculated through a line 10 and heat interchanger 12 into a lich oilheater 14. The rich oil is heated to a suiliciently high temperature tovaporize the C2 and higher hydro'- carbons which are to be recovered andthis rich oil is passed through a line 16 and flashed into themidportion of a rich oil rectifying still 18.

The rich oil rectifying still is preferably a bubble cap still whichwill permit the C2 land higher hydrocarbons to pass overhead and cutthrough a line 88 while causing the absorption oil to pass downwardlythrough the still. The C2 and higher hydrocarbons pass from the vaporline to a condenser 82 and the condensate is cllected in an accumulator84. Part of the condensed hydrocarbons is circulated by pump 86 and line88 up to the top of the still 18 to act as reflux. A

slightly higher pressure is maintained in the still 18 and accumulator84 than is maintained in the absorber 48 to assist in separating C2 andhigher boiling hydrocarbons from the absorption oil and to force C2 andhigher boiling hydrocarbon vapors through the line |82 and into thetower 48.

When the condensate is flashed in the chamber 58 substantial amounts ofthe lower boiling hydrocarbons are removed therefrom and the remainingcondensate passes from the tank through a line 98 up to the top of thebubble cap contactar at the top of the accumulator 84 to join the bodyof C2 and higher hydrocarbons in the accumulator. From the accumulatorthe hydrocarbon distillate may be removed through pump 92 and passthrough a line to a. fractionating still where the individualhydrocarbons may be fractionally separated.

When the desired C2 and higher hydrocarbons are removed from the richoil it becomes a lean oil which is Withdrawn from the bottom of thestill 18 through a line 94 and passed through the heat exchanger 12,then through a cooler 96 from which it is carried by means of a pump 98and forced through a line ill into the lines I8, 34 and 52 to supplylean absorption oil to the towers i6, 32 and 48,' respectively.

In the operation of the rectiiying still 18 some hydrocarbon vapors areformed and are separated from the distillate in the accumulator 84.These vapors which may contain a small amount of C1 but are composedprincipally of C2 and higher hydrocarbons, pass `outwardly through thecontacter countercurrent to the condensate to a line |02 and constitutethe vapors which are passed into the bottom of the stripping sectlon oftower 48 for the purpose of separating substantially all of the methanefrom the hydrocarbons passing through the contactor and tower 48.

In Figure 2 is illustrated an apparatus which is used for absorbing andseparating hydrocarbons from a gas which may be under a lower pressurethan the pressure of the gas which might be treated in the apparatusillustrated in Figure 1. 'This pressure may, for example, be from 200 to600 lbs. per square inch. In this apparatus gas is introduced through aline |0 into an absorber I6 and passes upwardly through absorption oilintroduced through a line I8. Methane separated from the gas passes outthrough a line 20 and valve 22. Rich oil from the bottom of the absorberI6 passes out through valve 24 and line 26, and flows through an inletline 60 into the bottom of the absorption section of a combined absorberand concentrating tower 48. Condensate from the gas is drawn in througha line 42 and is flashed into a ash tank 44. The flashing operationremoves substantially all of the C1 to C4 hydrocarbons, which vaporspass through a line 60 and join with the rich oil owing through. theline 26 into the tower 48. The distillate remaining in the tank 44,consisting of substantially all heavier hydrocarbons, is passed througha line 45 to the top of the bubble cap contactor tower on the top of theaccumulator 84. In the bubble cap section the condensate is furtherdistilled by the light vapors passing up through the section from theaccumulator to remove lighter hydrocarbons.

The vapors released from the rich oil from absorber I6 by pressurereduction, and vapor from tank 44 pass upwardly through the tower wherethe C2 and higher hydrocarbons are absorbed and methane is releasedthrough a line 62 and valve 64. Lean absorber oil is introduced into thetower 48 through a line 52 and passes downwardly through the tower anda. stripping section. Near the bottom of the stripping or concentrationsection hydrocarbon vapors are introduced through a line 66 which vaporsare composed principally of C2 and heavier hydrocarbons to displace themethane in the absorption oil and vapors passing through the tower 48.Rich oil which consists of a mixture of the enriched oil introducedthrough the line 52 and the rich oil from the absorber I6 pass out fromthe bottom of the tower 48 to a pump 68 and pass through a line `|0 andheat interchanger |2 into a rich oil heater '|4. The rich oil isdistilled in a rectifying still 'I8 in the same manner as that describedin connection with the distillation of rich oil in the apparatus ofFigure 1. The distillate which accumulates in accumulator 84 may bepassed through a pump 92 to a fractionating still to separate theindividual hydrocarbons. Vapors composed principally of C2 and heavierhydrocarbons pass from the top of the accumulator 84 through a contactorto a line |02 into the inlet 68 for the purpose of displacing methanefrom the condensate and the absorption oil in the tower 48.

It is emphasized that the return of the C2 and higher hydrocarbons intothe bottom of the combined absorber and concentrator acts Ytoconcentrate the propane and butane constituents which are recovered fromthe gas and at the same time displace the methane from the absorptionoil. With most of the gasoline treating lhydrocarbons while separatingthe methane.

systems a substantial portion of propane and butane is removed with themethane from the absorbers, but with the apparatus and method hereindescribed, a higher percentage of propane and butane may be recovered.Tests which have been made in the eld show that an average of ten tofifteen percent (and in some cases as high as fifty-eight percent) moreethane can be recovered than with the processes commonly in use.Further, an average of from three to ve percent (and in some cases morethan eleven percent) more propane may be recovered than with theprocesses commonly used.

In Figure 3 is illustrated an apparatus which is well adapted fortreating a gas for example of 50 to 400 lbs. for the recovery of C2 andhigher In this case the gas introduced through line |0 flows into thebottom of an absorbing section of a combined absorber and concentratortower 48. Lean oil is introduced into the top of the tower throug'h aline 52 and rich oil is removed from the bottom of the tower through apump |04 by which it is forced through a heat interchanger `|2 and richoil heater '|4. The absorption oil flows down through the tower 48 belowthe gas inlet and passes through a stripping section counter-current toa stream of hydrocarbon vapors introduced through an inlet 66 which aresupplied to the inlet through a line |02. The rich oil is distilled in astill 18. The C2 and higher hydrocarbons are accumulated in accumulator84. The vapors from the still and accumulator pass out through the line|02.

In Figure 4 is illustrated a type of combined absorber and concentratorwhich is well adapted for the purpose of treating two sources of gas,such as a lean natural gas and a rich natural gas, in order to recoverthe C2 and higher hydrocarbons and separate methane therefrom. The leangas which is composed principally of methane and a relatively smallamount of C2 and higher hydrocarbons is introduced into a combinedabsorber and concentrator |05 through a line |06 at the bottom of anabsorber section of the tower |05. At the same time rich gas, whichcontains a smaller amount of methane and a relatively larger proportionof C2 and higher hydrocarbons than is contained in the lean gas, isintroduced through a line |08 near the bottom of the stripping sectionof the tower |05. This gas passes upwardly through the stripping sectionto displace the methane and to concentrate the percentage of C2 andhigher hydrocarbons in the rich oil passing downwardly through the tower|05. The methane is removed from the top of the tower through line ||0and valve ||2 and rich oil is drawn out through a pump I4 by which itmay be circulated through a line H6 to pass into an absorber andconcentrator 48 to be treated in the tower 48 and still '|8, in the samemanner that has been described in connection with the treatment of richoil in Figures 1, 2 and 3.

The common practice for treating different types of natural gas whichcontain different amounts of C2 and higher hydrocarbons is to mix thegases and pass them into the bottom of an absorption tower. Comparativeresults in which an operation is carried out in which a lean and richgas are mixed and passed through the bottom of the tower and thetreatment of the same gas in the apparatus, such as illustrated inFigure 4, has shown the composition of the rich oil from the two typesof operation:

Gases mixed Mixture Rich as, Leen gas, Rich oil, M01 24 M01/24 ,{ajgM01/24 Hr. Hr. H Hr.

C1 1, 125 23, 301 24, 427 759 C: 467 2, 676 2, 143 524 01-.. 494 1, 6332, 127 1,077 104 89 311 400 380 N04 72 316 388 385 ICI. 14 91 105 105NCI 10 74 84 84 C|+ 2 94 96 96 Lean Oil 7. 866

Total 2. 274 28, 496 30 770 11. 276

Gas separate as shown in Figure 4 An important feature of the presentinvention resides in the separation of methane from other hydrocarbonsin the gas and the concentrations of light constituents, such as propaneand butane, in the hydrocarbons being absorbed from the gas. For eachmol of methane removed from a fractionator feed approximately fteen molsof propane or ve mois of ethane can be added to the vapor withoutchanging the vapor pressure of the fractionator feed. It will be seen,therefore, how important it is to remove even small quantities ofmethane and to replace it with ethane and higher hydrocarbons thusmaterially increasing the recovery of the C2 and higher hydrocarbons.

It will be noted also that the methane is eilectively separated from theother hydrocarbons of the gas and from the absorption oil without theuse of heat or stripping steam. The stripping of methane, from anabsorption oil at low temperatures is much more selective than whentreating an absorption oil which has been heated.

Furthermore the use of the combined absorber and concentrator permitsthe stripping of the methane from the absorption oil and gas without asmany pressure reducing stages or reabsorbers as is customarily used forthis purpose in commercial practice.

Tests have shown, furthermore, that a lesser amount (up to ten percentless) of lean oil is required for absorbing the hydrocarbons from gaswith the present invention than with the most eflicient absorptionsystem which has heretofore been used.

Although the combined absorber and concentrator 48 has been illustratedand described as a. single tower, it is obvious that the combined unitcould be made up as absorber unit and a separate stripping unit whereinthe gas would ow upwardly and the oil would ow downwardly first throughthe absorber unit and then through the stripping unit.

In the claims reference is made to the removal of C1 hydrocarbons fromthe top of the absorber and concentrator. It is to be understood thathydrogen and non-condensible gases, such as C0, CO2 and nitrogen, willbe removed with the methane if they are present. It is also to beunderstood that in commercial operatior of absorption and distillationequipment it is not practicable to separate all methane from the heavierhydrocarbons without leaving a small amount of hydrocarbons, such asethane and propane with the methane. With the present invention theamount of C2 and Cs hydrocarbons leaving the absorbers with the methaneis comparatively a very small amount.

The C2 and heavier hydrocarbons introduced into the base of thestripper, as referred to in the claims, are vapors recovered from thedistillation of a hydrocarbon mixture, said mixture having previouslyhad the methane separated therefrom. The still 18 and accumulator 84generally contain small amounts of methane and are operated so as topass C2 and heavier hydrocarbons from the accumulator and up through thebubble cap section to remove C1 and other xed gas from the condensateand hydrocarbon distillate in the accumulator. These C2 and heavierhydrocarbons may therefore contain a comparatively small amount ofmethane and fixed gas in it which will be separated in the absorber andconcentrator 48.

The preferred form of the invention having been thus described, what isclaimed as new is:

1. The method of separating C2 and higher hydrocarbons from highpressure gas comprising separating a condensate by retrogradecondensation from the gas, passing the uncondensed gas into the bottomof an absorption tower and upwardly through an absorption oil passingdown through the tower, removing substantially only Ci hydrocarbon fromthe top of the tower, removing a rich oil from the bottom of the tower,reducing the pressure on the rich oil and passing it into the bottom ofan absorption section of a second tower, passing absorption oildownwardly through the second tower to /join the rich oil from the firstabsorption tower, passing the resulting mixture of absorption oilsdownwardly through a stripping section of the second tower, introducingnear the bottom of the stripping section hydrocarbon vapors composedprincipally of C2 and higher hydrocarbons and passing the vaporsupwardly through the tower, removing substantially only C1 hydrocarbonfrom the top of the second tower, ashing the condensate with pressurereduction down to the pressure existing in the second absorption tower,passing vapors released from the condensate by the flashing operationinto the second tower with the rich oil from the iirst tower, removingthe rich oil mixture from the stripping section and distilling it torecover C2 and higher hydrocarbons overhead, partially condensing saidoverhead to produce a distillate and a lower boiling point vaporousfraction, passing said vaporous fraction into contact with the ashedunvaporized condensate to displace low boiling hydrocarbons therefromand to obtain said vapors composed principally of C2 and higherhydrocarbons which are introduced into the stripping section of thesecond tower.

2. The method of separating Cz and higher hydrocarbons from highpressure gas comprising: separating a condensate by retrogradecondensation from the gas, passing the uncondensed gas into the bottomof an absorption tower and upwardly through an absorption oil passingdown through the tower, removing substantially only C1 hydrocarbon fromthe top of the tower, removing a rich oil from the bottom of the tower,

flashing the rich oil under reduced pressure in an expansion chamber,separating vapors formed by the ashing and passing them through anabsorption oil of an intermediate absorption stage under the pressureprevailing in the expansion chamber, removing C1 hydrocarbon from theintermediate absorption stage, passing rich oil from the expansionchamber under reduced pressure into the bottom of an absorption sectionof a third tower, passing rich oil from the intermediate stage under thepressure prevailing in the third tower into the rich oil from theexpansion chamber owing into the third tower, passing absorption oildownwardly through the third tower to join the rich oil from theexpension chamber and intermediate stage, passing the resulting mixtureof absorption oils downwardly through a stripping section of the thirdtower, introducing near the bottom of the stripping section hydrocarbonvapors composed principally of C2 and higher hydrocarbons and passingthe vapors upwardly through the tower, removing substantially only C1hydrocarbon from the top of the third tower, ashing the condensate withpressure reduction down to the pressure existing in the third tower,passing vapors released from the condensate by the flashing operationinto the third tower with the flashed rich oil from the rst tower,removing the rich oil mixture from the stripping section and distillingit to recover C2 and higher hydrocarbons overhead, partially condensingsaid overhead to produce a distillate and a lower boiling vaporousfraction, passing said vaporous fraction into contact with the ashedcondensate to displace low boiling hydrocarbons therefrom and obtainsaid vapors composed principally of C2 and higher hydrocarbons which areintroduced into the stripping section of the second tower.

3. The method of separating C2 and higher hydrocarbons from highpressure gas comprising: separating a condensate by retrogradecondensation from the gas, passing the uncondensed gas into the bottomof an absorption tower and upwardly through an absorption oil passingdown through the tower, removing substantially only C1 hydrocarbon fromthe top of the tower, removing a rich oil from the bottom of the tower,ashing the rich oil into reduced pressure in an expansion chamber,separating vapors formed by the ashing and passing them through anabsorption oil in an intermediate absorption stage under the pressureprevailing in the expansion chamber, removing C1 hydrocarbon from theintermediate absorption stage, passing rich oil from the expansionchamber under a reduced pressure into the bottom of an absorptionsection of a third tower, passing rich oil from the intermediate stageunder the pressure prevailing in the third tower into the rich oil fromthe expansion chamber entering the second tower, flashing the condensatewith pressure reduction to the pressure existing in the intermediatestage, separating vapors from the flashed condensate and passing themthrough the absorption oil of the intermediate stage, again reducing thepressure on the condensate to the pressure in the third tower tovaporize lighter constituents in the condensate, passing the vapors oflighter constituents into the bottom of the absorption section of thethird tower, passing absorptionr oll downwardly through the i therefrom,

through a stripping section of the third tower, introducing near thebottom of the stripping section hydrocarbon vapors composed principallyof C2 and higher hydrocarbons and passing the vapors upwardly throughthe tower, removing substantially only C1 hydrocarbon from the top ofthe third tower, removing rich oil mixture from the stripping section,and distilling it to recover Cz and higher hydrocarbons overhead,partially condensing said overhead to produce a distillate and a lowerboiling vaporous fraction, passing said vaporous fraction into contactwith the flashed condensate from the second ashing operation to displacelow boiling hydrocarbons therefrom and obtain said vapors composedprincipally of C2 and higher hydrocarbons which are introduced into thestripping section of the said third tower.

4. A process of recovering C2 and higher hydrocarbons from high pressuregas containing methane comprising: separating a hydrocarbon condensatefrom the gas by retrograde condensation, passing the remaining gasthrough an absorber to absorb C2 and higher hydrocarbons in anabsorption oil, withdrawing methane from the absorber, reducing thepressure of the enriched absorption oil and passing it into anintermediate portion of a second absorber having absorption oil passingtherethrough, withdrawing methane from the top of the second absorber,flashing the condensate with pressure reduction to the pressureprevailing in the second absorber to release low boiling hydrocarbon gasand vapors introducing the released gas and vapors into said secondabsorber at an intermediate portion thereof, rectifying rich oilwithdrawn from the bottom of the second absorber to recover C2 andhigher hydrocarbons overhead, partially condensing said overhead toproduce distillate and a low boiling vaporous fraction, passing saidvaporous fraction directly into contact with the ashed condensate todisplace low boiling hydrocarbons therefrom, mixing the scrubbedcondensate directly with said distillate and introducing said lowboiling vaporous fraction into the bottom of said second absorber andpassing it upwardly therethrough.

GEORGE LOUIS GUDENRATH.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,789,470 Loomis Jan. 20, 19311,953,043 Cole et al Mar. 27, 1934 2,217,429 Balcar Oct. 8, 19402,237,386 Carney Apr. 8, 1941 2,249,885 Carney July 22, 1941 2,250,716Legatski July 29, 1941 2,265,845 Kuhl Dec. 9, 1941 2,288,453 Hill June30, 1942 2,290,957 Hachmuth July 28, 1942 2,337,254 Legatski et al Dec.21, 1943 2,345,934 Gregory Apr. 4, 1944 2,386,057 Noble Oct. 2, 19452,388,732 Finsterbusch Nov. 13, 1945 2,409,691 Noble Oct. 22, 19462,413,503 Katz Dec. 31, 1946 OTHER REFERENCES Harts: "Oil and GasJournal. Oct. 29. 1942, pages 59 to 61. 196-8.

